WYJ014-2004                               X70

1. The range

1.1 the technical conditions stipulated the west-east gas transmission project used in the manufacture of straight pipe of the submerged arc welding seam hot rolling steel material, manufacturing, testing, test and the related requirements, applicable to the project use API SPEC 5 L X70 steel grade straight seam submerged arc welding steel pipe manufacturing with 12.3 mm and 14.7 mm and 18.4 mm thickness of the steel plate.

1.2 plate size

Steel plate size (trimming) coincidence totable 1. But the purchase contract for the wide when otherwise stipulated, the contract provisions.

Table 1   Steel plate size

1.3 the technical conditions of the provisions of the steel manufacturing steel pipe applicable to transport conform to the requirements of the GB17820 type temperament of natural gas.

2. Chemical composition

2.1 chemical composition

According to the technical conditions of the supply of the chemical composition of the steel plate, including melting analysis and product analysis results should be consistent with the requirements of the table 3.

2.2 carbon equivalent

Carbon equivalent (Ceq) and cold crack sensitive coefficient (Pcm) should press type (1), (2) of calculation:

Ceq = C + Mn / 6 + (Mo + Cr + V) / 5 + (Ni + Cu) / 15 (1)

Pcm = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 B (2)

2.3 melting analysis

Every time a ausmelt smelting furnace should be melting analysis and provide report, chemical composition in steel must comply with the requirements of the table 2, and provide other intends to add the contents of the elements.

2.4 product analysis

Each time the production of ausmelt smelting furnace steel should be a finished product analysis, and provide report.

2.5 acceptance

If a melt furnaces times of chemical composition of 5.1 is not in conformity with the requirements, the GaiYing melt furnaces of time made all steel plate steel shall be rejected.

3. Mechanical properties

The tensile properties of 3.1

The results of tensile test should be consistent with the requirements of the table 3.

Table 2 Melting analysis and product analysis requirements（weight percentage）

Table 3  tensile property

3.2 bending test

3.2.1 manufacturers should take steel horizontal bend specimens do 180 °bending test, apex diameter of 2.0 t, (t for nominal thickness).

3.2.2 bend specimens of surface crack no stretch.

3.3 the fracture toughness

3.3.1 manufacturers should from the steel horizontal sampling, according to the API 5 L supplemental requirements SR-6 and API RP 5 L3 DWTT tear to test (DWTT), test conditions and acceptance requirements, see table 4.

Table 4  DWTT（weight tear test）The smallest percentage of shear area

3.3.2 Manufacturers should take 3samples from the horizontal of steel according to the API 5 L supplemental requirements SR-5 B in charpyimpact test.

doing charpyimpact testwhen the temperature is －20℃, the charpyimpact energy and shear area percentage should be consistent with the requirements of the table 6.

Table 6 the requirement of charpy impact test in －20℃

3.3.3 trace during the production manufacturer in shall be submitted to 5% of ausmelt smelting furnace times than transverse summer impact test plate shear area and absorbing energy toughness of brittle transition curve, ductile to brittle transition curve should be at least contain the following experiment temperature:

20 ℃, 0 ℃,-10 ℃, 20 ℃,-40-60 ℃,-℃

3.4 hardness

Steel horizontal section hardness value is the maximum allowed for 260 HV10.

4. Size, weight, length and allow deviation

4.1 thickness allow deviation

Thickness allow deviation should be 1.5 t % ~ + 0.8 t % (t for nominal thickness). All steel plate thickness should be not less than the average value of nominal thickness.

The thickness of the steel plate with a poor should be no more than 0.6 mm.

4.2 length allow deviation

The length of the steel plate deviation 0 ~ + 200 mm.

4.3 width deviation

Trimming the width of the steel plate after deviation is 0 ~ + 10 mm.

4.4 pingdu

Steel plate pingdu deviation shall not be more than 15 mm / 2000 mm.

4.5 appearance trimming steel should be cut into right Angle, cut inclined than 10 mm, curved sickle than 15 mm, and shall not make the length and the width of less than steel regulation size, must ensure that the order of the size of the smallest provisions of the rectangle.